Effect Of Slots Research Articles

Simulation of pulse width modulation strategies: validation based on sound quality evaluations

Though the noise emitted by an electrical machine is less loud than the one from a combustion engine, the existing literature shows it is not always more pleasant. This is because of its strong tonal content, due to deterministic excitations (e.g. electromagnetic slotting and switching effects, mechanical gear mesh effects). The main source of magnetic noise is the radiation of the stator submitted to electromagnetic forces, which are harmonic by nature. Their highest frequency components are generated by the Pulse Width Modulation (PWM) technique designed to vary the supply frequency and operating speed of the electric machine. Several PWM strategies exist, leading to specific harmonic spectra. A temporal simulation model has been developed to auralize the corresponding electromagnetic noise emitted by the machine, considering its mechanical and electrical parameters. A testbench has been adapted to test the relevance of the model, both from an electrical and acoustic point of view. The simulation model and the testbench can be used to generate virtual and real sound stimuli to be assessed in a jury testing. The subjective evaluations allow to assess the relevance of the auralization model, but also to identify the least annoying strategies.

Dopamine mediates a directionally opposite correlation between empathy and the reinforcing effects of amphetamine and gambling in people with gambling disorder vs. healthy controls

Understanding the relationship between empathy, subjective effects of addictive reinforcers and dopamine function in people with gambling disorder (PGD) vs. healthy controls (HCs) may inform GD treatment. The current investigation addressed this issue via retrospective analysis of data from three studies using amphetamine and a slot machine (SLOTS) as reinforcers in PGD and HCs. The Empathy scale of Eysenck's Impulsiveness Questionnaire assessed trait Empathy. The Gamblers Beliefs Questionnaire assessed cognitive distortions. The Eysenck Lie scale assessed socially desirable responding. PET scans quantified dopamine receptor expression and amphetamine-induced dopamine release in Study 1. Pre-treatment with the D2-receptor (D2R)-preferring antagonist, haloperidol or D1R-D2R antagonist, fluphenazine before SLOTS tested the role of D2 autoreceptors and post-synaptic D2R in Study 2. Pre-treatment with the multi-system indirect dopamine agonist, modafinil before SLOTS assessed the reliability of correlations in PGD. Striatal D2R expression predicted greater Empathy and lower amphetamine ‘Liking’ in HCs, and predicted greater symptom severity in PGD. Empathy predicted lower ‘Exciting’ effects of SLOTS under placebo in HCs; no correlation emerged under either antagonist. Relative to placebo, haloperidol decreased, whereas fluphenazine increased, the positive correlation between Empathy and Exciting effects of SLOTS in PGD. Modafinil markedly reduced the positive correlation between Empathy and Exciting effects of SLOTS seen under placebo in PGD. Empathy predicted greater cognitive distortions in PGD in all studies. Lie scale variance influenced several primary effects. Prior research linking the insula with Empathy, reactivity to interoceptive signals for risky rewards (uncertainty), and cognitive distortions, provides a parsimonious account for these results.

Numerical investigation into effects of slot control on flow around wind turbine blades

This paper investigates the effects of slots on wind turbine blade sections on the reduction of fluid loads on the airfoil in turbulent flows. The governing conversation equations were discretized using the finite volume method (FVM), numerically simulating an unsteady flow with a turbulent regime. It was found that slots at ΨA70° and high angles of attack (AOAs) improved the aerodynamic performance of the airfoil and delayed the stall by 2°. The Cl-Cd ratio was 31.49%, 79.22%, and 29.66% higher in the slotted airfoil than in the non-slotted one at an AOA of 18°, 20°, and 22°, respectively. Furthermore, slots with ΨA70° at AOAs of 20° and 22° substantially reduced lift and drag variations on the airfoil.

A hybrid analysis method for calculating the cogging torque of consequent pole hybrid excitation synchronous machine

PurposeWhen solving the cogging torque of complex electromagnetic structures, such as consequent pole hybrid excitation synchronous (CPHES) machine, traditional methods have a huge computational complexity. The notable feature of CPHES machine is the symmetric range of field-strengthening and field-weakening, but this type of machine is destined to be equipped with a complex electromagnetic structure. The purpose of this paper is to propose a hybrid analysis method to quickly and accurately solve the cogging torque of complex 3D electromagnetic structure, which is applicable to CPHES machine with different magnetic pole shapings.Design/methodology/approachIn this paper, a hybrid method for calculating the cogging torque of CPHES machine is proposed, which considers three commonly used pole shapings. Firstly, through magnetic field analysis, the complex 3D finite element analysis (FEA) is simplified to 2D field computing. Secondly, the discretization method is used to obtain the distribution of permeance and permeance differential along the circumference of the air-gap, taking into account the effect of slots. Finally, the cogging torque of the whole motor is obtained by using the idea of modular calculation and the symmetry of the rotor structure.FindingsThis method is applicable to different pole shapings. The experimental results show that the proposed method is consistent with 3D FEA and experimental measured results, and the average calculation time is reduced from 8 h to 4 min.Originality/valueThis paper proposes a new concept for calculating cogging torque, which is a hybrid calculation of dimension reduction and discretization modules. Based on magnetic field analysis, the 3D problem is simplified into a 2D issue, reducing computational complexity. Based on the symmetry of the machine structure, a modeling method for discretized analytical models is proposed to calculate the cogging torque of the machine.

Poisoned trap trees: a positive or negative tool to control Ips cembrae?

Ips cembrae is a destructive forest pest attacking European larch. In 2021 and 2022, effectiveness of poisoned trap trees, trap logs and slot traps baited with the Cembräwit in trapping I. cembrae was tested. The negative impact on the predators of genus Thanasimuswas evaluated. We found that poisoned trap trees and logs are more effective in trapping I. cembrae than slot traps. The aggregation of bark beetles on the trap log edge was significantly lower than in the central part, where the pheromone lure was placed. The application of poisoned trap trees is possible in cases of extreme outbreaks.

Effect of Blade Slot Positioning Close to Blade Root on the Performance of Highly Loaded Helium Compressor

Effect of Blade Slot Positioning Close to Blade Root on the Performance of Highly Loaded Helium Compressor

THE EFFECT OF DIFFERENT DIELECTRIC MATERIALS ON RADIATION FEATURES OF SLOTTED PATCH ANTENNAS FOR 6G COMMUNICATION SYSTEMS

In this study, patch antenna structures with rhombic shaped slots have been investigated for 6G communication systems. Four different dielectric materials, such as arlon, polyamide, polyimide, and silicon, have been selected for antennas with the same design procedure. In this way, the effects of slots on frequency responses for different dielectric substrates have been searched. The slots are parametrically analyzed in terms of edge size and location, and the designs are completed for values with the lowest return loss levels. The amount of return loss reduction in slotted antennas is 38% and 42% for arlon and polyamide, respectively, while the reduction is 28% and 8% for polyimide and silicon, respectively. In addition, bandwidth increases in slotted antennas vary according to the dielectric substrate material. The bandwidth increases have been 0.05 GHz, 0.426 GHz, 0.839 GHz, and 0.475 GHz for arlon, polyamide, polyimide, and silicon substrates, respectively. With these results, the study will give an insight to the researchers who will design antennas in 6G bands in terms of the effects of materials on antenna characteristics and will give inspiration for new designs.

General 2-D Analytical Framework for No-Load Analysis of Interior Permanent Magnet Machines

Solving two-dimensional (2-D) Maxwell’s equations in interior permanent magnet (IPM) motors is fairly complex due to the asymmetrical geometry of rotor magnets in the cylindrical coordinate system. This paper presents a general imaging solution to enable the 2-D open-circuit modeling of the family of IPM machines. Interior magnets are replaced/modeled with (i) virtual magnets on the surface of the rotor body (mapping interior magnets to the surface of the rotor body), and (ii) virtual volume current on the surface of the rotor body. The specifications of the virtual magnet (i.e., the remnant flux density) and the virtual volume current (i.e., current density level) are determined via magnetic circuit model. Next, the 2-D flux distribution of the transformed machines are calculated by solving 2-D Maxwell’s equations and considering relevant boundary conditions. Meanwhile, the effect of stator slots on flux profile is accounted by injecting proper amount of surface magnetizing current on the stator bore. Analytical results are supported via finite element method (FEM) and a series of experimental measurements.

Optical Slot-Assisted Metasurface for IgG Protein Detection

The sensing of antigens plays a pivotal role in the early diagnosis of tumors by potentially revealing specific biomarkers associated with them. Early detection of tumors can facilitate targeted and less invasive therapeutic strategies. In the realm of Immunoglobulin G (IgG) protein detection, a high concentration may indicate tumor lesions or the presence of symptoms commonly detectable just through invasive diagnostic methods. IgG detection is feasible in blood samples or other biological fluids like saliva or urine. These non-invasive tests offer the advantage of being repeatable over time, reducing the need for invasive or painful procedures. In the pursuit of next-generation medical technologies aimed at flexible and compact sensing platforms, we proposed a refractometric system mainly based on a dielectric metasurface, operating at about 780 nm, featuring a 2D distribution of cells composed of dimers that support the optical slot effect. This effect allows for a large Q-factor, with a small footprint, and strong spatial confinement. Specifically, a Q-factor of 3.19 × 103 with a significant amplitude (> 0.7 a.u.) enables a sensitivity of 25 nm/RIU for IgG protein detection.

The influence of electromagnetic field models on the damper winding loss and heat calculation results of tubular hydro‐generator

AbstractThis study investigates the effect of electromagnetic field models on tubular hydro‐generator damper winding losses and heat calculations using an on‐site 36‐MW such generator as an example. Sinusoidal steady‐state and transient‐motion electromagnetic field models were established to analyze damper winding losses and heat. Results indicate that, despite exhibiting a substantially higher computational efficiency than the transient‐motion electromagnetic field time‐stepping FE model, the sinusoidal steady‐state electromagnetic field FE model does not comprehensively and reasonably consider several key factors, such as tooth and slot effects, the main magnetic field, and the armature reaction. Consequently, the magnetic field, damper bar loss, and heat derived from this model exhibit considerable deviations from the on‐site generator observations. In comparison, the transient‐motion electromagnetic field time‐stepping FE model, owing to its ability to consider these influencing factors, provides more comprehensive and reasonable results.

Speed Estimation of Induction Motor at Low and Zero Speed using High Frequency Signal Injection for Rotor Slot Harmonics Detection

Rotor position estimation based on high frequency signal injection method represents the interesting way to provide the high performances of the AC drives sensorless controlled at low or near zero speed range. So, this method requires the existence of saliencies inside the IM particularly the presence of the slots where their design constitutes the main advantageous to exploit its effect for rotor speed monitoring. First, the present paper exposes a model of the induction machine including slotting effects which it can be exploited in order to extract the harmonic saliency created by rotor slotting. Second, the high frequency signal injection method is used in order to allow tracking the characteristic harmonic saliency due to rotor slotting from which the rotor position and speed may be estimated. A High frequency voltage signal injection creates a high frequency current modulated by the saliencies presented inside the machine. To extract information about rotor position, the resulting stator current treads to heterodyning process to eliminate the disturbance components and subsequently the rotor position may be extracted by a closed-loop observer. Simulation results are shown in order to verify the validity of the proposal and to confirm the effectiveness of estimation method at zero frequency.

Analytical Design Methodology for Wind Power Permanent Magnet Synchronous Generators

In this paper a novel analytical design methodology for wind power permanent magnet synchronous generators is presented. This kind of electric generator plays a major role in small-scale wind energy conversion systems up to 10 kW. The proposed diameter-cubed sizing equation is based both on the generator requirements, imposed by the application, and the design parameters that rely on the designer criteria. The magnetic field waveforms of both the permanent magnets field and the armature field are considered from the first moment through the winding factors, as well as the slots effects given by the Carter factor. The analytical model of the permanent magnet synchronous generator is validated with the finite element method, showing good agreement, both with no load and under load. As the generator is unsaturated, the main source of divergence between the analytical and the finite element model are the iron losses, due to the nonuniform magnetic field distribution.

Blue-band slot-enhanced nanobeam cavity with porous-GaN cladding

Traditional photonic crystal cavities are hard to simultaneously attain extreme temporal and spatial confinement of light, which remains a barrier to realize ultimate control of light in a material and maximum performance in photonic devices. Here we demonstrated GaN and porous-GaN based photonic crystal nanobeam cavity by improving the confining light properties with the application of the slot and anti-slot effects. Three dimensional finite-difference time-domain simulations show that the cavity for blue band possesses ultrahigh quality factor as 1.67 × 107, and the mode volume is reduced tenfold compared to nanobeam without slot and anti-slot.

Design of Planar Antennas in Ku- and S/C-Bands Using the Fibonacci Slot

In this paper, the Fibonacci slot is configured for Ku- and S/C -band antenna applications. In the Ku-band antenna, the slot is placed on the patch and the desired band is achieved by a rectangular omega-shaped slot etched out from the lower ground plane. While in the S/C band antenna, the Fibonacci slot is etched out from the ground plane. With the size of 55 × 40 mm2, the Ku-band antenna operates from 13.04∼17.68 GHz. The S/C band antenna of size 30 × 30 mm2 has a band from 3.55 to 6.07 GHz. A peak gain of 6 and 3.8 dBi is noted from the Ku- and S/C band antenna, respectively. Parametric analysis is done to analyze the effect of slots. The antennae are validated experimentally through impedance bandwidth plot, radiation pattern, and gain. Simulated and experimental results are compared for both antennae and a good match is observed between them.

Structure and characteristic analysis of a novel magnetic bearing without thrust disk

Conventional thrust magnetic bearing (TMB) uses large thrust disk to generate axial levitation force. However, due to the existence of thrust disk, it will lead to many problems in assembling and dynamic balance. Moreover, it will even limit rotational speed. In order to solve these shortcomings, a novel TMB with uniform teeth on the stator and rotor is proposed. It replaces the conventional thrust disk with staggered teeth structure between the stator and rotor. This paper obtains analytical expressions of levitation force, current stiffness and displacement stiffness of the novel TMB by equivalent magnetic circuit method and method of air–gap ratio permeance. Considering slot effect between the teeth of stator and rotor, its influence is analyzed by finite-element analysis (FEA) and the expression of displacement stiffness has been modified. The simulation and experiment results show that the proposed TMB can ensure enough bearing capacity by reasonably designing the staggered distance between the teeth of stator and rotor. In addition, under the reasonable tooth structure, TMB can achieve self-recovery ability by utilizing the influence of slot effect on levitation force. Compared with conventional TMB, the proposed TMB has greater advantages in assembly, dynamic balance and high speed. It will be conducive to its application in medical, aerospace and other fields.

Aerodynamic performance of flapping wing with alula under different kinematics of complex flapping motion

The flight of birds is a remarkable feat, and their remarkable ability to fly derives from complex multi-degree-of-freedom flapping motions and small-scale feather structures that have evolved over millions of years. One of these feather structures is the alula, which can enhance the birds’ flight performance at low speeds and large angles of attack. Previous studies on the alula have focused on the steady state. This undoubtedly ignores the unsteady effect caused by complex flapping motion, which is also the most important characteristic of avian flight. Therefore, this paper carries out a study on the effect of different motion modes and motion parameters on the aerodynamic mechanism of the alula. Previous studies found the dominate effect in the lift enhancement is influenced by Reynolds number, stall condition and geometric parameters. After coupling complex flapping motion, aerodynamic characteristics of the flapping wing are greatly influenced by different motion patterns and parameters. For pure plunge motion, both the slot effect and the vortex generator effect of the alula dominate the lift enhancement; while for plunge-twist and plunge-sweep motion, the vortex generator dominates more. At a low plunge amplitude, a low twist amplitude and a low sweep amplitude, the deflection of the alula has a good lift enhancement compared with the baseline wing. Increasing these amplitudes attenuates both the slot effect and the vortex generator effect. The alula can enhance the lift by 10.4% at the plunge amplitude of 25 deg (for pure plunge motion), by 7.9% at the plunge amplitude of 25 deg and twist amplitude of 10 deg (for plunge-twist motion), by 3.3% at the plunge amplitude of 25 deg and sweep amplitude of 15 deg (for plunge-sweep motion). Meanwhile, at a large sweep phase angle, the alula has a better lift enhancement. Increasing the phase angle enhances the vortex generator effect of the alula, and it has an optimal lift enhancement effect of 11% at the phase angle of 180 deg.

Design and Analysis of a Low-profile Microstrip Antenna for 5G Applications using AI-based PSO Approach

Microstrip antennas are high gain aerials for low-profile wireless applications working with frequencies over 100 MHz. This paper presents a study and design of a low cost slotted-type microstrip patch antenna that can be used in 5G millimeter wave applications. This research focuses on the effect of ground slots and patch slots which, in turn, affect different antenna parameters, such as return loss, VSWR, gain, radiation pattern, and axial ratio. The working frequency range varies from 24 to 28 GHz, thus falling within 5G specifications. A subset of artificial intelligence (AI) known as particle swarm optimization (PSO) is used to approximatively solve issues involving maximization and minimization of numerical values, being highly challenging or even impossible to solve in a precise manner. Here, we have designed and analyzed a low-profile printed microstrip antenna for 5G applications using the AI-based PSO approach. The novelty of the research is mainly in the design approach, compactness of size and antenna applicability. The antenna was simulated with the use of HFSS simulation software.

Magnetic Field Analysis and Thrust Optimization of Arc Permanent Magnet Synchronous Motor Combined With Linear Mover and Arc Stator

The intelligent annular transmission system driven by permanent magnet synchronous linear motor (PMSLM) is composed of linear and arc segments. When the mover enters the arc segment from the straight segment, the coupling area between the primary and secondary becomes smaller. It results in that the average thrust decreases and the thrust ripple increases. This phenomenon affects the control accuracy and operation reliability. This paper focuses on the research on the arc permanent magnet synchronous motor (A-PMSM) in the arc segment of the annular transmission system. The equivalent magnetic network model of A-PMSM is established. The air-gap coefficient is used to compare the slot effect of arc primary structure with that of straight primary structure. The influence of arc radius and radial width on the slot effect of A-PMSM with linear mover is obtained. The structure of magnetic pole, the radial width of secondary and the slot width are optimized by the combination of hierarchical optimization and orthogonal optimization. The A-PMSM's performance of thrust is optimized, which provides experience for the design of the motor in the annular transmission system.

Investigation of aerodynamic performance of Clark-Y airfoil with more realistic tubercle model and internal slots

An experimental study is conducted to research the combined effect of leading-edge (LE) tubercles and internal slots on the Clark-Y airfoil at Reynolds numbers (Re) of 5.0×104, 7.5×104, and 1.0×105 for angles of attack ranging from 0° to 30°. The Clark-Y is a cambered airfoil that performs well at low and medium Reynolds numbers, having a maximum thickness of 11.7% at 28% of the chord. Five different test models are the subjects of experiments, one of which is the baseline. The other test models are the Wavy model, which has LE tubercles, and the Wavy with three different slot positions: the Wavy-LES (leading-edge slot), the Wavy-MS (middle slot), and the Wavy-TES (trailing-edge slot). The LE tubercle geometry is formed by the sum of two sinusoidal wave functions with a realistic approach. In the present work, experimental studies are performed through force measurements, and detailed information on a 3-dimensional flow field is obtained by a surface-oil flow visualization technique. Force measurements indicate that the Wavy model delays stall and exhibits smoother stall behavior compared to the baseline. Moreover, the findings show that the lift coefficient (CL) of the Wavy model deteriorates in the pre-stall region with the inclusion of the internal slots but improves significantly in the post-stall region. Maximum improvement in CL in the post-stall region was achieved by 60% in Wavy-LES at Re of 5.0×104 as compared to the baseline. At Re of 5.0×104, Wavy and Wavy-MS present a better lift-to-drag ratio (CL/CD) than the other models in the pre-stall region, whereas the baseline is the best at Re of 1.0×105. The best CL/CD is achieved by Wavy-LES in the post-stall region, regardless of the Reynolds numbers. The variation of flow characteristics relevant to aerodynamic performance is revealed by surface oil flow visualization for all tested models.

An Analytical Method for Determining Flux Density in Surface-Mounted Permanent Magnet Machines with Unequal Magnetic Poles

An analytical method was proposed for obtaining the magnetic field distribution for surface-mounted permanent magnet machines with the structure of unequal magnetic poles. Firstly, the Laplace equation and Poisson equation were solved using the method of the separation of variables, and then the mathematical model of the motor structure with unequal magnetic poles was obtained. Secondly, according to the design parameters of the two types of prototypes motors, the flux density in the air gap region of the two types of prototypes motors was calculated, respectively. Thirdly, by comparing the results calculated using the analytical method with the results obtained using the finite element method, the analytical method proposed in this paper was proven to be effective. Moreover, the armature reaction field and the effect of the stator slotting were considered in the mathematical model as well. Overall, the analytical method presented in this paper provides a theoretical basis for the analytical calculation of motors with the structure of unequal magnetic poles.